Images

This is how it looks. There is the outer area which is the difference between the FSA and the Inner cone oulet area.

Hi CEtorca,

I think you will find that splitting the flows between the annular outlet and the cone will result in large losses in thrust.
If the annular outlet is too large the flow out of it will be following a greatly expanding area with a converging cone in the center causing the airflow to slow more than you expect which will result in poor thrust. The fluid will flow thru the path of least resistance so the annular outlet will need to be restrictive to force the fluid thru the conical outlet. It would be better to use the cone to control airflow for enhanced thrust, having two outlets will double the losses. It might need to be a little larger than scale but the performance will not deteriorate like the annular design and it won't be noticeable in flight.

could you not just go for a "profile" cone instead? just a flat sheet from the side and the bottom in an vertical "X". this way, it'll look like the real thing from the side and from the bottom as it's flying over you. this way, you'll just have one opening instead of two and it'll be less restrictive.

I think you will find that splitting the flows between the annular outlet and the cone will result in large losses in thrust.
If the annular outlet is too large the flow out of it will be following a greatly expanding area with a converging cone in the center causing the airflow to slow more than you expect which will result in poor thrust. The fluid will flow thru the path of least resistance so the annular outlet will need to be restrictive to force the fluid thru the conical outlet. It would be better to use the cone to control airflow for enhanced thrust, having two outlets will double the losses. It might need to be a little larger than scale but the performance will not deteriorate like the annular design and it won't be noticeable in flight.

Eric B.

Eric, it's a very wise advise and I've been thinking about it. What I came up yesterday, was to set up a test bench with the annular oulet and the center cone ,where the Red motor fairing shown in the graph is displaced horizontaly so you can control the amount of flow entering the converging cone. Measuring thrust and power you can determine where is the best position where the air is not slow to much due to the effect you explained. Then compare the results with the bench test without any of the cones, just the EDF itself and see if the losses are significant.

Images

could you not just go for a "profile" cone instead? just a flat sheet from the side and the bottom in an vertical "X". this way, it'll look like the real thing from the side and from the bottom as it's flying over you. this way, you'll just have one opening instead of two and it'll be less restrictive.

like this

yes, it looks like complete crap, since I don't do CAD at all. and also, it looks like crap on the model too, but it's a compromise you may have to live with, unless you make a scale cone that is removable for flight. that's of course, if you find out that your thrust is too low with the setup as you have it drawn up. if it works, you'll be ok. just pointing out other options that might be used.

Images

Eric, it's a very wise advise and I've been thinking about it. What I came up yesterday, was to set up a test bench with the annular oulet and the center cone ,where the Red motor fairing shown in the graph is displaced horizontaly so you can control the amount of flow entering the converging cone. Measuring thrust and power you can determine where is the best position where the air is not slow to much due to the effect you explained. Then compare the results with the bench test without any of the cones, just the EDF itself and see if the losses are significant.

Never hurts to put it to the test. Please post your numbers it will be interesting.